Probes are mechanical tools for measuring electrical characteristics of microscopic electronic devices (e.g., semiconductor devices). As well known, a semiconductor device has pluralities of pads for communicating signals with an external electronic system. The semiconductor device processes an operation with electrical signals that are input through the pads and then transfers a processed result to an external system through the pads. During this, the probes are arranged on a printed circuit board of a probe card, physically contacting with the pads, so they form electrical paths for signal transmission with the external device or system.
Meanwhile, with higher integration density in semiconductor devices, the pads become narrower in interval and smaller in size. Since the probes should be formed to contact physically with the pads, the change of pad structure, which is required by the increase of integration density, causes technical difficulties relevant to structure and arrangement of the probes. For example, the probes have to be arranged with assuring the minimum interval so as to prevent electrical interference and short-circuit between them.
In order to reduce contact resistance between pads and probes, an over-drive contacting scheme should be used to connect the probes with the pads. (Here, the over-drive contacting scheme is a connecting method in which a pressure beyond a required magnitude is applied to the probes.)
However, since a contact pressure in the over-drive contacting scheme results from a distortion of the probes and a resultant restoring force, a repetition of over-drive contacts may cause permanent deformation in shape of the probes. Such deformation of the probes may reduce the restoring force of the probe or cause a variation of arrangement of the probes. To lessen these problems, the probes are required of having sufficiently large restoring force.
According to prior arts, a cantilever-type probe card has been proposed in order to enhance the restoring force of probe. (See FIG. 1.) In the cantilever-type probe card 90, bumps 92 arranged on a substrate 91 are bonded to one ends of supporting beams 93. Tips 94, which are contacted directly with pads of an electronic device, are bonded to the other ends of the supporting beams 93. In the meantime, the tips 94 contact to the pads under pressure, and the supporting beams 93 need to have restoring force by elasticity. At this time, a length of supporting beam 93 should be sufficiently long, for a required restoring force. If a length of supporting beam is insufficient, the elasticity of supporting beam 93 is too weak to offer a sufficient restoring force.
Therefore, supporting beams for the cantilever-type probe card should have a sufficient length, and a distance between the bumps, which are bonded to the supporting beams, should be increased to satisfy the requirement related to the length of supporting beam.
In addition, it needs to minimize an interval between probes of the probe card for inspecting the highly integrated semiconductor devices of today.